人体寄生虫学课件：Introduction to Trematoda

1、Introduction to Trematoda(吸虫纲概述)Phylum Platyhelminthes (扁形动物门), Class Trematoda (吸虫纲), Order Digenea (复殖目):1. Most adult trematodes are dorso-ventrally flattened, bilaterally symmetric, leaf-shaped or tongue-like.2. All of them have two suckers, an oral sucker and a ventral sucker.3. The digestive t

2、ract is degenerate. The end of intestine is a cecum without anus.4. The reproductive system is developed and hermaphroditic. (cross-fertilization is common)malereproductive systemfemalereproductive system5. Excretory system includes flame cells, capillaries, collecting tubules and an excretory bladd

3、er.6. Eggs of most species have an operculum (lid, 盖) and/or a small spine (knob). The developed egg contains a miracidium (毛蚴) .7. They are biohelminths. Eggs continue to develop in fresh water. Their intermediate hosts are in the water. The first intermediate hosts are all snails and the second in

4、termediate hosts vary from species to species.8. Alternation of generation is present in their life cycles.9. Life cycle:adult - eggs - miracidium (毛蚴) -sporocyst (胞蚴)-redia (雷蚴)- cercaria(尾蚴)- metacercaria (囊蚴) - adult10Infective stage is usually a metacercria.11. They all have their reservoir host

5、s, so fluke diseases are zoonosis.* Blood fluke is a special fluke.Clonorchis sinensis(华支睾吸虫)Clonorchis sinensis, also name liver fluke, parasitizes in the intrahepatic bile ducts (肝内胆管). The worm was named because of its branched testes.The infection usually results from eating raw or non-well-cook

6、ed fresh water fish.I. Morphology1. Adultsunflower seed-like (葵花籽样);10-25 mm 3-5 mm;the oral sucker is slightly larger than the ventral sucker;two deeply branched testes in tandem are located in the posterior 1/3 part of the bodyvitelline glands (卵黄腺) are in the lateral fields;genital pore (生殖孔) is

7、in the front of the ventral sucker;the pouch-liked excretory bladder (排泄囊) opens at the posterior end. 2. Egg2917 m, the smallest helminth egg;looks like sesame (芝麻) under the low power and a water melon seed under the high power;yellow brown in color;operculum, shoulder, knob;the content is a mirac

8、idium (毛蚴).II. Life cycle30 days120 days2035 days1st intermediate host: bithyniasporocyst (胞蚴)redia (雷蚴)cercaria (尾蚴)2nd intermediate hostFresh water fish of Family Cyprinidae (鲤科)Pseudorasbora parva 麦穗鱼,Cyprinus carpio 鲤鱼,Aristichthys nobilis 大头鱼,Mylopharyngodon piceus 青 鱼metacercaria (囊蚴)round or

9、ellipse,about 0.138 mm * 0.115mm,two layers of wall,suckers, excretory bladder, intestinal cecum (肠支).II. Life cycleInfective stage: metacercariaRoute of infection: by mouth-eating raw infected with metacercariaeSite of inhabitation: intrahepatic bile ductsIntermediate hostFirst intermediate hosts:

10、bithynia (豆螺)Second intermediate hosts: fresh water fish and shrimps Reservoir hosts: cat, dogLife span: 20-30 years. III. PathogenesisLiver flukes live in bile passages (mechanical and chemical irritations)Inflammation of biliary epithelium Fibrosis of the passage wall and mechanical obstruction du

11、e to worms Bile stream blockage High pressure in bile ducts, bacterial infection an excess of bile in hepatic ducts Cholangitis, Cholancysititis, Degeneration of local hepatic cells calculus of bile duct Necrosis of local hepatic cells Regeneration of the damaged tissue Biliary cirrhosis (the liver

12、gets hard and green) Portal v. Hypertension, function failure liver cancerClinical manifestation(1) Low-grade infection: no symptom(2) General case: poor appetite, fullness in abdomen, diarrhea, physical weakness, hepatic pain, hepatomegaly,eosinophilia.(3) Severe case: icterus (黄疸), systemic toxemi

13、a (毒血症), chill, fever, vomiting, dizziness, mental disorder, emaciation (消瘦), ascites (腹水), palpitation (心悸). The patients may die of coma, infective complications, hemorrhage of upper part of digestive tract.(4) In child case: physical and mental growths are retarded. 海蛇头IV. Diagnosissymptoms + sig

14、ns + history of eating raw fish and shrimp.etiologic examination:1. first choice: sample: stool examinationmethod: water sedimentation method (水洗沉淀法) or alkali digestive method (NaOH 45%) (氢氧化钠消化法)2. duodenal draining (十二指肠引流液)immunologic tests are for reference only.V. Epidemiology1. The liver fluk

15、e is widely distributed in Asia (China, Japan, Korea, Thailand, Kampuchea, Vietnam, etc.).2. In China it is found in 25 provinces, cities and autonomic regions except Xinjiang, Gansu, Inner Mongolia. It is widely prevalent in Shandong Province.3. Epidemiological survey:habits of eating raw fishmode of growing fishreservoir hostsintermediate hosts (snail, fish, shrimp) .VI. Treatment and preventioneliminate source of infection:treat both the pat